Differences in binding sites of 2-azido-4-nitrophenol have been noted between hamster brown adipose and liver mitochondria. Interaction between those binding sites and those of carbodiimides will be examined, and the effects of pretreatment with various fatty acids and fatty acid analogs will be explored. The purpose of these studies is to gain insight into association of proteins related to tight coupling of oxidation with phosphorylation in mitochondrial inner membranes and how such association is affected by fatty acids and the synthetic reagents described.